The use of silicon in devices, such as n-p-n bipolar transistors, is well known. Equally well known is the time dependent degradation of these devices, which is caused by reverse-bias stress of the emitter-base junction of the n-p-n transistors. Reverse-bias stress results in the degradation of the common-emitter current gain (H.sub.FE =.DELTA.I.sub.C /.DELTA.I.sub.B). However, it is thought that the collector current (I.sub.C) is not affected by the stress, but an increase in the recombination component of the base current at low V.sub.BE has been observed. In BICMOS and BINMOS circuits this reverse-biasing will result in a long term performance degradation and eventually circuit failure. It is believed that the nature of the damage mechanism is that hot carriers generated in the reverse-biased base-emitter junction create interface trap states on the base oxide by breaking silicon/hydrogen, often referred to as the hot carrier degradation effect. More specifically, it is believed that the base-oxide damage (interface trap generation) is caused by the interaction of hot electrons with the Si/SiO.sub.2 interface. Electrons that are generated by band-to-band (from the valence band to the bottom of the conduction band) tunneling at the base-emitter junction are subsequently accelerated (heated) by the junction electric field. In most cases, the substrate, as well as other structures within the device, comprises silicon, and the defects are thought to be caused by dangling bonds (i.e., unsaturated silicon bonds) that introduce states in the energy gap, which remove charge carriers or add unwanted charge carriers in the device, depending in part on the applied bias. While dangling bonds occur primarily at surfaces or interfaces in the device, they also are thought to occur in the bulk oxide. To alleviate the problems caused by such dangling bonds, a hydrogen passivation process has been adopted and has become a well-known and established practice in the fabrication of such devices.
In the hydrogen passivation process, it is thought that the defects that affect the operation of semiconductor devices are removed when the hydrogen bonds with the silicon at the dangling bond sites. While the hydrogen passivation process eliminates the immediate problem associated with these dangling bonds, it does not eliminate degradation permanently because the hydrogen atoms that are added by the passivation process can be "desorbed" or removed from the previous dangling bond sites by the hot carrier effect.
A hot carrier is an electron or hole that has a high kinetic energy, which is imparted to it when voltages are applied to electrodes of the device. Under such operating conditions, the hydrogen atoms, which were added by the hydrogen passivation process, are knocked off by the hot electrons. This hydrogen desorption results in aging or degradation of the device's performance. This hot carrier effect is particularly of concern with respect to smaller devices, such as a bipolar transistors.
Accordingly, what is needed in the art is a bipolar transistor device and a method of manufacture therefore that does experience the level of efficiency degradation experienced by the devices that are passivated with conventional hydrogen passivation processes. The present invention addresses these needs.